.el-button-group el-button:first-child .el-button{
    border-top-left-radius: 5px;
    border-bottom-left-radius: 5px;
}

.el-button-group el-button:last-child .el-button{
    border-top-right-radius: 5px;
    border-bottom-right-radius: 5px;
}

.el-button-group {
    /* background-color: red; */
    border-color: red;
}